Package for transporting or enclosing radioactive materials

ABSTRACT

Package for transporting or enclosing radioactive materials emitting a large amount of heat, having a heat protection device provided between a container metal casing and an external jacket. The device comprises concentric rows of radial metal vanes between which an endothermic insulating material is placed, so that heat emitted by the radioactive material is discharged under optimum conditions, whilst the endothermic material forms an effective heat barrier against external heat.

United Stat Bochard PACKAGE FOR TRANSPORTING OR ENCLOSING RADIOACTIVEMATERIALS Camille Bochard, Lyon, France Assignee: Robatel S.L.P.I.,Genas, France Filed: Dec. 14, 1973 Appl. No.: 424,720

Inventor:

US. Cl 250/506; 250/515 Int. Cl. G2lf 3/00; G2lf 5/00 Field of Search250/428, 429,506, 507,

References Cited UNITED STATES PATENTS 3/1969 Nash et al 250/5063,466,662 9/1969 Blum 250/506 51 Dec. 30, 1975 3,727,060 4/1973 Blum250/506 Primary ExaminerArchie R. Borchelt Attorney, Agent, orFirmDowell and Dowell [57] ABSTRACT Package for transporting orenclosing radioactive materials emitting a large amount of heat, havinga heat protection device provided between a container metal casing andan external jacket. The device comprises concentric rows of radial metalvanes between which an endothermic insulating material is placed, sothat heat emitted by the radioactive material is discharged underoptimum conditions, whilst the endothermic material forms an effectiveheat barrier against external heat.

16 Claims, 3 Drawing Figures PACKAGE FOR TRANSPORTING OR ENCLOSINGRADIOACTIVE MATERIALS The present invention relates to improvements madeto packaging intended to enclose and/or transport radioactive materialssafely.

It is known that packages of the type in question generally comprise aninternal container placed inside an anti-radiation shield (of lead or asimilar material). This shield is itself surrounded by an externalprotective jacket made of metal, which, however, provides an annularspace forming a seat for a fire protection device.

Experience has shown that this fire protection device must possesscertain characteristics, some of which appear to be contradictory:

Firstly, under normal conditions of use, this protective device mustpossess very good heat conductivity, so that the heat emitted by theradioactive material contained in the packaging can be discharged and sothat any overheating of the shield, made of lead or another material,can be avoided.

On the other hand, it is vital that, should there be strong source ofexternal heat, such as a fire in the vicinity of the package, theprotective device should possess very low conductivity so that it canform a screen and effectively prevent any overheating of the shield;however, after the fire the conductivity should remain adequate todischarge the internal heat once more.

In order to fulfil these two conditions, it has been proposed to producethe fire protection device by filling the annular space provided betweenthe shield and the jacket with a mass of an insulating product ofendothermic nature, consisting either of calcium sulphate (CaSO .%H O)as described in French Pat. No. 1,438,241 of 21 Oct. 1964, or of amixture formed by a suspension of aluminium trihydrate (AI O .3H O) andiron or mild steel powder in water, as claimed in French Pat. No. 6927,633 (publication No. 2,055,761) of 12, Aug. 1969.

In spite of the advantages offered by such insulating products, a veryawkward disadvantage is still encountered. In order to ensure good heatdischarge, it is obviously advantageous to reduce the thickness of theinsulating mass, whilst in order to ensure that the shield is insulated,the abovementioned mass must, on the other hand, have as large a volumeas possible. In practice, a compromise must therefore finally be adoptedwhich does not perfectly satisfy either one or the other of theabovementioned conditions.

The aim of the improvements which form the subject of the presentinvention is more especially to deal with the abovementioneddisadvantage and to allow a package to be produced which can contain aradioactive material emitting a large amount of heat, under optimumsafety conditions.

In accordance with the invention, the fire or heat protection devicecomprises two concentric rows of metal vanes oriented to extendradially, withcircumfer- ,ential spaces between the vanes of rows beingfilled with an endothermic insulatingmaterial.

It will be understood that such an arrangement makes it possible to givethe endothermic insulating material as large a volume as desired; themetal vancs of the two concentric rows ensure effective discharge of theheat emitted by the radioactive material enclosed in the container,whatever the abovementioned volume may be.

' In accordance with a preferred embodiment of the invention, the metalvanes consist of lateral flanges or wings, the profiles of which have aU-shaped cross-section, which are made of copper or of another metal ofgood heat conductivity. The two rows of vanes and the endothermicinsulating material which they contain are held between two annularlayers of a heat swellable material (of the type of hydrated calciumsulphate) which is a good heat conductor, so that the said vanes areeffectively sealed and that heat is transmitted between the variousannular layers in use.

The attached drawing, which is given by way of an example, will allowthe invention, the characteristics which it displays and the advantageswhich it can provide to be better understood:

FIG. 1 is a transverse cross-section of a packaging comprising theimprovements according to the invention. I

FIG. 2 represents a part of FIG. 1 on a larger scale to show thearrangement of the fire protection device.

FIG. 3 is a similar view to FIG. 2, but corresponds to an alternativeembodiment.

The packaging represented in FIG. 1 comprises, in the customary manner,an internal container 1 which has a circular transverse cross-sectionand is embedded inside a shield or screen 2 made of lead or of anothermaterial, which is itself cylindrical in shape. The shield 2 issurrounded by an external protective jacket 3 made of steel or ofanother resistant metal; the said jacket 3 provides, between itsinternal wall and the shield 2, an annular space forming a seat forafire protection device shown schematically at 4.

As shown more clearly in FIG. 2, this heat or fire protection device 4comprises afirst external row or ring of profiled sections 5 which havea U-shaped protile in transverse cross-section; these profiled sections5, for example made of copper, extend over the entire height of thepackage and are joined one to another by welding points 5'. The lateralflanges or wings of each profiled section 5, which is held in contactwith lateral flanges or wings of adjacent profiled section 5, thusdefine vanes which are oriented radially toward the inside of thecontainer; the transverse web or bridge of the profiled section which isperforated at intervals at 5a, being turned toward the jacket 3. Theprotective device also comprises a second internal row or ring of vanesconsisting of angle-profiles 6 preferably made of copper, and joined toone another at 6. The angleprofiles 6 are oriented in such a way thatone of their wings is placed radially inside a profiled section 5, thetwo rings being wedged together by means of grooved plates or rods 7made of wood or of another material which possesses a high coefficientof heat insulation. The spaces provided between the vanes of the tworings 5 and 6 are filled with a mass 8 of a material which is ofendothermic nature and can absorb a large amount of heat when subjectedto an abrupt rise in temperature. The tworings are sealed in place bymeans of internal and external annular layers 9 of a material whichprovides good heat contact.

As shown at the beginning of this text, the mass 8 can be produced inaccordance with one or other of the two French Pat. Nos. 1,438,241 and69 27,633. The following composition (by volume) can be used to form thesealing layers 9:

the whole being mixed with 25% of water relative to the volume of drymixture.

It will be understood that the heat emitted by the radioactive materialheld in the internal container 1 is transmitted to the shield 2 andpasses through the internal annular layer 9. The ring formed by theangleprofiles 6 is thus heated to a high temperature; the heat cannot bedischarged radially to the outside as a result ofthe heat barrier formedby the wedges or rods 7, so that the heat must pass through each mass 8to reach the lateral wings of the profiled sections which discharge intothe atmosphere through the external annular layer 9 and the metal jacket2. It will be understood that the heattransmission between the internalring and the external ring is achieved under excellent conditions as aresult of the low circumferential thickness of each of the masses 8 andof the large exchange surface thereby created.

.vapourise, so that the angle-profiles 6 are only heated to a verymoderate degree. Any danger of the shield 2 becoming accidentallyoverheated is thus avoided; the volume of the endothermicinsulatingmaterial can be made greater by increasing the radial length of thevanes of the two rings of the fire protection device, and thissimultaneously improves the heat insulation of the packaging and theheat discharge characteristics as a result of the increase in theexchange surface,

During the heating of themasses 8 of endothermic insulating material bya surrounding fire, the steam generated can escape through theperforations 5a of the profiled sections 5 and escape to the outsidethrough orifices provided for this purpose in the jacket 3;theseorifices are normally closed by fusible stoppers 3a;

P16. 3 illustrates another embodiment of the invention according towhich the shield 2 is lined with a protective neutron screen 10. In sucha case, the angleprofiles 6 comprise a very long radial wing so as todefine a space for a suitable material. Use can especially be made of acomposition of the following type (the percentages here being given byweight):

polyethylene granules 38% hydrated alumina (Al,O .3H O) l8% colemanite(2CaO.3B O .5H O) 7% cement l4% plaster 7% water As a variant, thescreen 10 can consist of a row of bundles formed by polyethylenefilaments of small diameter, oriented parallel to each other and coated,for example, by immersion, with a boron-containing binder which, afterdrying, seals them into the spaces provided between the angle-profiles6. In practice, the screen can have the following composition (byweight):

polyethylene filaments 75% colemanite 7% cement 6% plaster 5% water 7%This embodiment makes it possible to produce a solid material which isvery effective from the point of view of protection against neutrons andis of low density (close to that of water).

It is seen in all cases that the screen 10 does not in any way disturbthe discharge of heat emitted by the radioactive material, since theangle-profiles 6 provide excellent heat conductivity; the heat isdissipated in the same way as in FIG. 2, through the external ring ofthe profiled sections 5, the layer 9 and the jacket 3.

It should furthermore be understood that the preceding description isonly given by way of an example and that it in no way limits the scopeof the invention, which would not be exceeded by replacing the detailsof execution which have been described by any other equivalent means. Itshould in particular be noted that the insulating mouldings 7 can bereplaced by a layer of suitable insulating material.

I claim:

1. Packaging for enclosing and transporting radioactive material of thetype including a material container surrounded by an anti-radiationshield located within a protective metal jacket whose inner wall isspaced from the outer wall of the shield to leave an annular spacebetween said walls for housing an improved protective device operativeto insulate the container against heat generated externally of thepackaging, the improvement comprising:

a. first and second metal rings concentrically disposed in said annularspace and spaced from each other, the first ring being disposed in heatconductive relationship with said jacket and the second ring beingdisposed in heat conductive relationship with said shield:

b. radially inwardly extending vanes fixed to the first ring andextending toward the second ring without contacting the latter, andradially outwardly extending vanes fixed to the second ring andextending toward the first ring without contacting the latter, theradially inwardly extending vanes alternating with the radiallyoutwardly extending vanes; and

c. endothermic insulating material filling the spaces between theadjacent vanes.

2. Packaging according to claim 1, wherein one of the rings comprises anannular series of mutually attached U-shaped sections each having twolegs joined by a web, and the legs of the adjacent sections beingradially disposed to form vanes.

3. Packaging according to claim 1, wherein oncof the rings comprises anannular series of mutually attached angle sections, each having aradially disposed leg forming a vane and an annularly disposed leg forming a part of the ring.

4. Packaging according to claim 1, wherein the spacing between adjacentvanes is no greater than the radial length of a vane, and whereininsulating material is interposed between the free end of each va'ne andthe opposite ring toward which it extends, whereby to prevent heatconductive contact therebetween.

5. Packaging according to claim 4, wherein said insulating materialcomprises a plate having one side lying against a ring and having anopposite side grooved to receive a vane, said plates wedging thealternating vanes together in accurately maintained relationship.

6. Packaging according to claim 1, wherein said rings are supportedwithin said annular space by heat-conductive sealing material disposedbetween the first ring and the jacket and between the second ring andthe radiation shield.

7. Packaging according to claim 6, wherein the sealing material includeshydrated calcium sulphate.

8. Packaging according to claim 6, wherein the sealing materialcomprises, by volume, substantially:

Metal Billets 50% Cast Cement 33% Reinforced Plaster [7% the whole beingmixed with about 25% of water relative to the volume of the dry mixture.

9. Packaging according to claim 1, wherein the vanes of the second ringare radially longer than the vanes of the first ring, leaving a zonebetween the rings wherein the vanes are not alternately opposed, andsaid zone being filled with neutron absorbing material packed betweenthe vanes of the second ring to form a neutron screen.

10. Packaging according to claim 9, wherein said neutron absorbingmaterial comprises series of bundles each formed of polyethylenefilaments coated with a boron-containing binder; the binder joining thebundles to one-another and sealing them between the vanes.

11. Packaging according to claim 10, wherein said neutron absorbingmaterial has substantially the following composition by weight:

Polyethylene Filaments Colemanite 7% Cement 6% Plaster 5% Water 7%.

12. Packaging according to claim 1, wherein the first ring comprises anannular series of attached U-shaped sections, each having two legsjoined by a web and the legs of adjacent sections being radiallyinwardly disposed to form vanes; and wherein the second ring comprisesan annular series of attached angle sections, each having a radiallydisposed leg forming a vane and an annular disposed leg forming a partof the second ring; and the free ends of the vanes being spaced from theopposed ring by insulating material, whereby to prevent heat conductivecontact between the vanes and the opposing rings.

13. Packaging according to claim 12, wherein said insulating materialcomprises plates wedged between the vanes and the opposing rings andgrooved to receive the ends of the vanes.

14. Packaging according to claim 12, wherein the rings are supportedwithin said annular space by heat conductive sealing material disposedbetween the first ring and the jacket and between the second ring andthe radiation shield.

15. Packaging according to claim 14, wherein the sealing materialincludes hydrated calcium sulphate.

16. Packaging according to claim 12, wherein the vanes of the secondring are radially longer than the vanes of the first ring, leaving azone between the rings wherein the vanes are not alternately opposed,and said zone being filled with neutron absorbing material packedbetween the vanes of the second ring to form a neutron screen.

1. Packaging for enclosing and transporting radio-active Material of thetype including a material container surrounded by an anti-radiationshield located within a protective metal jacket whose inner wall isspaced from the outer wall of the shield to leave an annular spacebetween said walls for housing an improved protective device operativeto insulate the container against heat generated externally of thepackaging, the improvement comprising: a. first and second metal ringsconcentrically disposed in said annular space and spaced from eachother, the first ring being disposed in heat conductive relationshipwith said jacket and the second ring being disposed in heat conductiverelationship with said shield: b. radially inwardly extending vanesfixed to the first ring and extending toward the second ring withoutcontacting the latter, and radially outwardly extending vanes fixed tothe second ring and extending toward the first ring without contactingthe latter, the radially inwardly extending vanes alternating with theradially outwardly extending vanes; and c. endothermic insulatingmaterial filling the spaces between the adjacent vanes.
 2. Packagingaccording to claim 1, wherein one of the rings comprises an annularseries of mutually attached U-shaped sections each having two legsjoined by a web, and the legs of the adjacent sections being radiallydisposed to form vanes.
 3. Packaging according to claim 1, wherein oneof the rings comprises an annular series of mutually attached anglesections, each having a radially disposed leg forming a vane and anannularly disposed leg forming a part of the ring.
 4. Packagingaccording to claim 1, wherein the spacing between adjacent vanes is nogreater than the radial length of a vane, and wherein insulatingmaterial is interposed between the free end of each vane and theopposite ring toward which it extends, whereby to prevent heatconductive contact therebetween.
 5. Packaging according to claim 4,wherein said insulating material comprises a plate having one side lyingagainst a ring and having an opposite side grooved to receive a vane,said plates wedging the alternating vanes together in accuratelymaintained relationship.
 6. Packaging according to claim 1, wherein saidrings are supported within said annular space by heat-conductive sealingmaterial disposed between the first ring and the jacket and between thesecond ring and the radiation shield.
 7. Packaging according to claim 6,wherein the sealing material includes hydrated calcium sulphate. 8.Packaging according to claim 6, wherein the sealing material comprises,by volume, substantially:
 9. Packaging according to claim 1, wherein thevanes of the second ring are radially longer than the vanes of the firstring, leaving a zone between the rings wherein the vanes are notalternately opposed, and said zone being filled with neutron absorbingmaterial packed between the vanes of the second ring to form a neutronscreen.
 10. Packaging according to claim 9, wherein said neutronabsorbing material comprises series of bundles each formed ofpolyethylene filaments coated with a boron-containing binder, the binderjoining the bundles to one-another and sealing them between the vanes.11. Packaging according to claim 10, wherein said neutron absorbingmaterial has substantially the following composition by weight: 12.Packaging according to claim 1, wherein the first ring comprises anannular series of attached U-shaped sections, each having two legsjoined by a web and the legs of adjacent sections being radiallyinwardly disposed to form vanes; and wherein the second ring comprisesan annular series of attached angle sections, each haVing a radiallydisposed leg forming a vane and an annular disposed leg forming a partof the second ring; and the free ends of the vanes being spaced from theopposed ring by insulating material, whereby to prevent heat conductivecontact between the vanes and the opposing rings.
 13. Packagingaccording to claim 12, wherein said insulating material comprises plateswedged between the vanes and the opposing rings and grooved to receivethe ends of the vanes.
 14. Packaging according to claim 12, wherein therings are supported within said annular space by heat conductive sealingmaterial disposed between the first ring and the jacket and between thesecond ring and the radiation shield.
 15. Packaging according to claim14, wherein the sealing material includes hydrated calcium sulphate. 16.Packaging according to claim 12, wherein the vanes of the second ringare radially longer than the vanes of the first ring, leaving a zonebetween the rings wherein the vanes are not alternately opposed, andsaid zone being filled with neutron absorbing material packed betweenthe vanes of the second ring to form a neutron screen.